The immune system synthesizes antibodies for the protection of the body from viruses, bacteria and allergens. To respond to different particles, the body synthesizes different immunoglobulins or antibodies. For instance, there is one antibody for mononucleosis and a different antibody for chickenpox. Autoimmune diseases are a different case wherein the body, at times, mistakenly, produces antibodies against itself, where it mistakes healthy tissues and organs for foreign particles.
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Antibodies are of different types and they are –
- Immunoglobulin A (IgA)
- Immunoglobulin G (IgG)
- Immunoglobulin M (IgM)
- Immunoglobulin E (IgE)
- Immunoglobulin D (IgD)
IgM
- These are primarily seen in lymph and blood fluid
- These are the first antibodies the body synthesises when it combats a new infection or to new “non-self” antigens which render a short-term protection
- It increases for a few weeks and then dips due to the initiation of production of IgG
IgG
- These are the most common antibodies – about 75-80% of the immunoglobulins in the blood are IgG
- They can be seen in the blood and other fluids of the body
- They are involved in protection against viral and bacterial infections
- These antibodies can take time for formation once an immunisation or infection occurs
- These antibodies lay the foundation for long-term protection against microorganisms
- These antibodies are the only type of antibodies that are capable of crossing the placenta in a pregnant woman to help protect her fetus
Key Differences between IgM and IgG
The table below depicts the differences between IgM and IgG.
|
IgM |
IgG |
|
Size |
|
|
Largest antibodies |
Smallest antibodies |
|
Location |
|
|
Found in blood and lymph fluids |
Found in all body fluids |
|
Their approximate percentage compared to all the antibodies in the body |
|
|
5-10% |
75-80% |
|
When are they produced post- infection? |
|
|
Detected 4-7 days after infection starts |
Produced 7-14 days post-infection and are detected for weeks, months, even years later |
|
Life span |
|
|
Short-lived |
Often persist for life |
|
Occurrence |
|
|
Typically come up earlier on the emergence of an infection – early stages |
Formed later than IgM antibodies – later stages |
|
Subclasses |
|
|
Absent |
Present. Four classes – IgG1, IgG2, IgG3, IgG4 |
|
Number of antigen-binding sites |
|
|
10 |
2 |
|
Role |
|
|
Involved in cytosolic reactions and agglutination |
Associates with isotopes, activates the complement system |
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